Chemical modification of Aspergillus niger ß-glucosidase and its catalytic properties.

Aspergillus niger ß-glucosidase was modified by covalent coupling to periodate activated polysaccharides (glycosylation). The conjugated enzyme to activated starch showed the highest specific activity (128.5 U/mg protein). Compared to the native enzyme, the conjugated form exhibited: a higher optimal reaction temperature, a lower Ea (activation energy), a higher K m (Michaelis constant) and Vmax (maximal reaction rate), and improved thermal stability. The calculated t 1/2 (half-life) values of heat in-activation at 60 °C and 70 °C were 245.7 and 54.5 min respectively, whereas at these temperatures the native enzyme was less stable (t 1/2 of 200.0 and 49.5 min respectively). The conjugated enzyme retained 32.3 and 29.7%, respectively from its initial activity in presence of 5 mM Sodium Dodecyl Sulphate (SDS) and p -Chloro Mercuri Benzoate ( p -CMB), while the native enzyme showed a remarkable loss of activity (retained activity 1.61 and 13.7%, respectively). The present work has established the potential of glycosylation to enhance the catalytic properties of ß-glucosidase enzyme, making this enzyme potentially feasible for biotechnological applications.

Chemical modification of Aspergillus niger β-glucosidase and its catalytic properties

Aspergillus niger β-glucosidase was modified by covalent coupling to periodate activated polysaccharides (glycosylation). The conjugated enzyme to activated starch showed the highest specific activity (128.5 U/mg protein). Compared to the native enzyme, the conjugated form exhibited: a higher optimal reaction temperature, a lower Ea (activation energy), a higher Km (Michaelis constant) and Vmax (maximal reaction rate), and improved thermal stability. The calculated t1/2 (half-life) values of heat in-activation at 60 °C and 70 °C were 245.7 and 54.5 min respectively, whereas at these temperatures the native enzyme was less stable (t1/2 of 200.0 and 49.5 min respectively). The conjugated enzyme retained 32.3 and 29.7%, respectively from its initial activity in presence of 5 mM Sodium Dodecyl Sulphate (SDS) and p-Chloro Mercuri Benzoate (p-CMB), while the native enzyme showed a remarkable loss of activity (retained activity 1.61 and 13.7%, respectively). The present work has established the potential of glycosylation to enhance the catalytic properties of β-glucosidase enzyme, making this enzyme potentially feasible for biotechnological applications.

Evaluation of noninvasive versus invasive techniques for the diagnosis of Helicobacter pylori infection.

BACKGROUND: Helicobacter pylori is one of the most common bacterial strains causing chronic infections, affecting over one half of the world's population. There is increasing interest in noninvasive methods for diagnosing H. pylori infection. The aim of the study was to evaluate 3 different noninvasive methods of diagnosis: the stool antigen test (HpSA), the serum antibody test, and the stool-polymerase chain reaction (PCR) test as against invasive methods based on histopathologic diagnosis. MATERIALS AND METHODS: Gastric biopsies were obtained during endoscopy. Sections were stained with hematoxylin and eosin and Giemsa stain. Serum samples were tested for H. pylori antibody using an enzyme-linked immnunosorbent assay kit for the semiquantitative determination of IgG antibodies; stool samples were tested for H. pylori antigen using polyclonal enzyme-linked immnunosorbent assay kits. DNA samples from stool specimens were extracted, followed by PCR for the detection of H. pylori UreA. RESULTS: The results revealed that 18/19 (94.7%) patients were positive for H. pylori infection as detected by Giemsa stain, and 84.2% were positive on the basis of hematoxylin and eosin stain, with a sensitivity and specificity of 88.9% and 100%, respectively. Diagnosis by noninvasive methods, including the serum antibody test, revealed a sensitivity and positive predictive value of 88.9% and 94.2%, respectively, whereas the stool antigen test recorded a sensitivity and positive predictive value of 72.2% and 92.9%, respectively. The stool-PCR test recorded a sensitivity of 72.2% and specificity of 100%. CONCLUSIONS: Among the noninvasive methods for diagnosis of H. pylori infection, the 3 methods used in this study recorded promising results, including good sensitivity, which was the highest in the serum antibody test, whereas the stool-PCR test recorded excellent specificity.

Chronic hepatitis c genotype-4 infection: role of insulin resistance in hepatocellular carcinoma.

BACKGROUND: Hepatitis C virus (HCV) is a major cause of chronic hepatitis and hepatocellular carcinoma (HCC) and different HCV genotypes show characteristic variations in their pathological properties. Insulin resistance (IR) occurs early in HCV infection and may synergize with viral hepatitis in HCC development. Egypt has the highest reported rates of HCV infection (predominantly genotype 4) in the world; this study investigated effects of HCV genotype-4 (HCV-4) on prevalence of insulin resistance in chronic hepatitis C (CHC) and HCC in Egyptian patients. METHODS: Fifty CHC patients, 50 HCC patients and 20 normal subjects were studied. IR was estimated using HOMA-IR index and HCV-4 load determined using real-time polymerase chain reaction. Hepatitis B virus was excluded by enzyme-linked immunosorbent assay. Standard laboratory and histopathological investigations were undertaken to characterize liver function and for grading and staging of CHC; HCC staging was undertaken using intraoperative samples. RESULTS: HCC patients showed higher IR frequency but without significant difference from CHC (52% vs 40%, p = 0.23). Multivariate logistic regression analysis showed HOMA-IR index and International Normalization Ratio independently associated with fibrosis in CHC; in HCC, HbA1c, cholesterol and bilirubin were independently associated with fibrosis. Fasting insulin and cholesterol levels were independently associated with obesity in both CHC and HCC groups. Moderate and high viral load was associated with high HOMA-IR in CHC and HCC (p < 0.001). CONCLUSIONS: IR is induced by HCV-4 irrespective of severity of liver disease. IR starts early in infection and facilitates progression of hepatic fibrosis and HCC development.